Emerging dental CAD/CAM systems provide a powerful technology for rapid fabrication of quality restorations from ceramics. However, the clinical performance of this brittle class of materials is strongly influenced by surface and subsurface defects produced during fabrication. In the clinical context, defects from machining operations (as well as those from contact fatigue and wear) can lead to premature clinical failures. The overall objective of Project 1 is to establish the relationship between intrinsic microstructural characteristics and machining parameters and environment on surface integrity (smoothness as well as surface and subsurface damage) of ceramics for dental restorations. The objective of this project will be accomplished through the six specific aims. Aims 1-3 will focus directly on surface integrity, quantifying surface integrity as a function of machining parameters (Aim 1), machining environments (Aim 2), and materials microstructure (Aim 3). Aim 4 is to elucidate the mechanisms of material removal during machining of ceramic materials as a function of material microstructure, providing a knowledge base for future investigations. Aim 5 will address the problem of tool wear, quantifying tool wear as a function of machining parameters, machining environment, and ceramic microstructure. An economic evaluation of machining operations for dental ceramics is determined in Aim 6. At the conclusion of this project, valuable information will have been obtained which will impact long-term clinical performance of machined ceramic restorations. This information is increasingly critical as the production of high quality, cost effective, ceramic restorations with a high probability of clinical success become more and more important as replacements for metal restorations are being sought and improved esthetics are being demanded by dental patients.